ABOARD THE USS SAIPAN (AP) _ U.S. Marines flew helicopters into rebel-held territory in Liberia on Monday to evacuate 97 foreign nationals, including at least four Americans, fleeing heavy fighting in the capital Monrovia.

The evacuees, who included the Spanish ambassador and the papal nuncio to Liberia, were airlifted during the morning from the port of Buchanan, which is controlled by rebel leader Charles Taylor's National Patriotic Front.

In addition to the Americans, the evacuees included at least 16 Spaniards, 15 West Germans, as well as smaller numbers of citizens of India, Lebanon, Switzerland, France, Britain, Holland and Guinea.

There were also 21 Liberians, mostly dependents of U.S. citizens.

''We are very happy to be here. Our trip was extremely difficult,'' said Manuel de Luna, the Spanish ambassador. His nervous face showed signs of relief as he sat in the admiral's parlor on board the Saipan, moored four miles off Buchanan for the evacuation operation.

The foreigners - many of whom sought refuge in the West German, Spanish and Italian embassies - had been trapped on the battle line in Monrovia's eastern suburbs, where heavy fighting broke out Friday after Taylor's forces attacked government troops. Rebels told local residents to leave the area.

The foreigners left Sunday night in a convoy bound for Buchanan, about 90 miles southeast of Monrovia.

The rebels insisted that the Marines arrive unarmed to carry out the evacuation from a beach in Buchanan.

While heavily armed rebel troops patrolled the beach, the evacuees waited in a tropical storm for the helicopters to carry them to safety.

Among those evacuated was Jeanette Carter of Colorado, who lectures in anthropology at the University of Liberia in Monrovia.

''People were petrified that the government forces would start using rockets to get the rebels out of the area'' in Monrovia's eastern suburbs, she said.

''We were frightened of being accused of being rebel sympathizers by the government. That was a realy worry in case the rebels withdrew from an area and the government forces returned,'' she said.

Efforts to ferry the evacuees on by helicopter from the Saipan to Freetown, Sierra Leone, had to be abandoned because of heavy rain.

U.S. Public Affairs Officer Matthew McGrath told reporters in Freetown that only eight of the evacuees were flown to the Sierra Leone capital on Monday.

The Saipan, an amphibious assault helicopter carrier, is one of four Navy ships off Liberia with a contingent of about 2,100 Marines.

More than 200 Marines were airlifted to Monrovia on Aug. 5 to evacuate Americans and protect the U.S. Embassy. Washington has said they would not intervene in the war in which rebels are seeking to oust President Samuel Doe.

Prior to Monday's operation, the United States had only evacuated those foreign nationals who could reach the U.S. Embassy in Monrovia. The Marines also rescued American employees at a Voice of America relay station and U.S. Omega ship-tracking station behind rebel lines after the evacuations began.